Preterm birth (PTB) is the major cause of neonatal morbidity and mortality in non-anomalous neonates. Nulliparous women are a particularly important and relatively understudied group at risk for PTB. They account for about 40% of pregnancies in the United States and are at increased risk for both medically indicated and spontaneous PTB. In addition, the rate of PTB in nulliparous women appears to be rising. Little is known about the mechanisms of PTB in these women since many studies of preterm (especially spontaneous) birth have focused on at risk populations based on a prior history of PTB. To address this knowledge gap, the NICHD is creating a network of clinical research sites to study multiple facets of PTB and adverse obstetric outcomes in nulliparous women. This Network will design and execute a prospective, longitudinal cohort study of 10,000 nulliparous women. The research protocols developed will determine characteristics that influence and/or predict adverse pregnancy outcomes in nulliparous women including genetics, epigenetics, physiological response to pregnancy, interaction with environmental exposures, fetal growth and development, and placental development and function. These studies will enhance our understanding of the mechanisms of adverse pregnancy outcomes and ultimately our ability for the future reduction in the rate of PTB. The University of Utah (UU) is exceptionally qualified to participate in this network. The proposed team of investigators has considerable scientific, clinical, and administrative capability and experience in multicenter clinical research and NICHD sponsored Networks relevant to maternal-fetal medicine. There is broad based, multidisciplinary expertise in clinical obstetrics, fetal imaging, perinatal pathology, genetics, genomics, proteomics and perinatal epidemiology. In addition, there is a unique, long-standing collaborative research relationship between the UU, community hospitals, and private Obstetric providers. Finally, there is excellent infrastructure for conducting translational and multicenter clinical research. This infrastructure, termed the Obstetrics and Gynecology Research Network, employs almost 70 experienced individuals allowing for flexibility, efficiency, and quality in the conduction of clinical research.